Ultrafast imaging of terahertz electric waveforms using quantum dotsMicroscopic electric fields gove
Ultrafast imaging of terahertz electric waveforms using quantum dots
Microscopic electric fields govern a remarkable variety of phenomena in condensed matter and their ultrafast evolutions drive plasmonics, phononics and highspeed nanoelectronics. Access to high-frequency electric waveforms is of crucial importance to diverse disciplines in nanoscience and technology, yet, microscopic measurements are still severely limited.
In a new paper published in Light: Science & Applications, a team of scientists, led by Prof. Georg Herink from the University of Bayreuth, Germany, and co-workers from the University of Melbourne, Australia, has introduced a new THz microscope for imaging ultrafast electric waveforms encoded in the visible luminescence of nanocrystal probes. Strong electric fields modulate the emission yield of nanocrystals and enable the detection of THz near-field waveforms by microscopy of visible photons in the far-field.
The researchers generated ultrafast electric fields inside gold structures using intense Terahertz pulses. A layer of semiconductor nanocrystals covering the samples is excited by ultrashort visible pulses and shows modulated visible emission depending on the momentary local THz electric field. Fundamentally, this probing of electric fields via luminescence yield is enabled by the quantum-confined Stark effect in quantum dots, generating the contrast mechanism of the scheme termed Quantum-Probe Field Microscopy (QFIM). While scanning the temporal delay between THz excitation and optical pulses, an optical fluorescence microscope captures snapshots of the modulated local emission and generates movies of the local fieldevolution.
